1. Field of the Invention
The present invention relates to a method of manufacturing a nozzle plate including nozzles each having straight sections and tapered sections.
2. Description of the Related Art
In general, an inkjet head of an inkjet recording apparatus includes a nozzle plate, in which nozzles (also referred to as “nozzle apertures”) are formed. The inkjet head performs recording onto a recording medium by ejecting droplets of ink respectively from the nozzles connected to pressure chambers by applying pressure to the ink inside the pressure chambers by using ejection energy applied by piezoelectric elements, heating elements, or the like, so as to deposit the ink droplets onto the recording medium.
A commonly known nozzle plate (also referred to as a “nozzle forming substrate”) is formed with nozzles, each of which has a nozzle opening in a surface (referred to as a “nozzle face”) of the nozzle plate, a straight section formed vertically extending from the nozzle opening perpendicularly to the nozzle face, and a tapered section substantially having a funnel shape, which is formed on an opposite side of the straight section from the nozzle opening and has a surface oblique to the straight section. Since a substantially right-angled step section is not present between the straight section and the tapered section, then even if the ink contains bubbles, the bubbles do not remain in the step section, and hence decline in the ejection performance is prevented. By this means, it is possible to achieve smooth ejection of ink droplets.
A nozzle plate of this kind is formed by a laminated substrate forming step, an etching window forming step, a first etching step and a second etching step, as described in Japanese Patent Application Publication No. 07-201806 (FIGS. 29 to 31), for example. In the laminated substrate forming step, a laminated substrate is formed by bonding a silicon substrate that has both planar surfaces along (100) crystal planes (hereinafter referred to as the “(100) substrate”) on a silicon substrate that has both planar surfaces along (110) crystal planes (hereinafter referred to as the “(110) substrate”). In the etching window forming step, etching windows are formed in the (100) substrate at positions where nozzles are to be formed. The region apart from the positions where the nozzles are to be formed is covered with a mask.
In the first etching step, anisotropic etching of the (100) substrate is carried out through the etching windows to form recesses in the (100) substrate. Each of the etched recesses has side surfaces, which are {111} surfaces exposed in the (100) substrate, and a quadrilateral bottom surface, which is an exposed upper surface of the (110) substrate (hereinafter referred to as the “quadrilateral upper surface of the (110) substrate”). Thereby, the etched recesses gradually narrowing from the (100) substrate toward the (110) substrate are formed. A tapered section of each of the nozzles is formed substantially in a quadrilateral pyramid shape in the (100) substrate, by the {111} surfaces defining each of the etched recesses in the (100) substrate.
In the second etching step, the (110) substrate is anisotropically etched from the quadrilateral upper faces of the (110) substrate, which have been exposed by the anisotropic etching in the first etching step. By the anisotropic etching in the second etching step, the (110) substrate is formed with quadrilateral holes. Each of the quadrilateral holes has side surfaces, which are {111} surfaces exposed in the (110) substrate by the anisotropic etching. Thereby, a straight section of each of the nozzles is formed in a quadrilateral hole shape in the (110) substrate and connected to the tapered section.
The tapered section and the straight section are thus formed coaxially by forming the straight section by etching the (110) substrate through the etched recess formed in the (100) substrate, in other words, by defining the positions of the tapered section and the straight section of the nozzle by a single photolithography process (i.e., the etching window forming step). As a result of this, positional deviation between the tapered section and the straight section is prevented.
Furthermore, since the tapered section and the straight section are respectively formed in the two substrates having the different crystal orientations, then by adjusting the thicknesses of the two substrates, it is possible to specify the lengths of the tapered section and the straight section (the lengths in the thickness direction of the nozzle plate). Consequently, the lengths of the tapered section and the straight section can be managed with high precision.